Composition for protecting metallic structures



, 2,935,412 COMPQSITIQN' FOR PROTECTING METALLIC STRUCTURES 2 Claims. (Cl. 106- 122) The present invention relates to the insulation and protection of metallic structures and particularly metallic structures which are buried in the earth, such as pipes,

conduits, and the like. In a more particular aspect, the

present invention relates to insulating and corrosion protective materials for buriedmetallic structures which are capable of being applied in a granular form and can then be modified by heating the metallic structure to form a plastic zone immediately adjacent the exterior surface of the structure, a sintered zone surrounding the plastic zone and a third zone of loose particles surrounding the sintered zone.

It has heretoforebeen known that various structures, such as pipe lines, could be insulated and protected against corrosion by applying a variety of coating materials, particularly asphalts and asphalts containing various mineral and non-mineral fillers. These coatings have generally been applied by a molding process comprising applying heat and pressure to a suitable coating com- United States Patent position either in the shop or in the field. In addition,

United States Patent No. 2,668,125 teaches that metallic structures may be effectively insulated by surrounding the metallic structure with a naturally-occurring asphaltic pyrobituminous material, such as gilsonite, in granular form and thereafter internally heating the metallic structure toform a plastic zone of bitumen on the surface of the structure, a sintered zone of bitumen surrounding the plastic zone and a zone of loose particles surrounding the sintered zone. It is this latter method of applying insulating and corrosion protective materials to which the present invention is particularly directed.' v g Although granular naturally-occurring bitumens are effective as'insulating materials when applied in accordance with the procedure described above, there are also certain disadvantages inherent in the use of materials of this-type. In the first instance, materials of this type are relatively expensive and must be used in quantities which make cost a serious factor. In addition, naturally-occurring bitumens by their very nature are non-uniform and vary greatly in their properties depending upon the source from which the material is obtained. For example; a natural bitumen from one source may be eminently suitable for its intended purpose while a similar material from a second source will exhibit properties so radically different that itv is entirely ineffective. In addition, a given bitumen from a single source may be suitable for use under a given set of conditions whereas this same material cannot be used under another set of conditions. Further, there is no way in which the suitability or non-suitability of a given material can be acc'urately predicted without resorting to actual coating and performance trials employing the exact conditions under whili' the material is to be used.

It is therefore an object of the present invention to provide a composition and method for insulating and protecting against corrosion metallic structures which coinposition is economical and uniform'innature. An-

2 other object of the present invention is to provide a composition and method for insulating and protecting against corrosion metallic structures wherein the prop erties of the composition can be substantially duplicated from batch to batch. Still another object of the present invention is to provide a composition and method for insulating and protecting against corrosion metallic structures wherein the properties of the material can be adjusted in a predetermined manner to meet the peculiar,

needs of any type of service. These and other objects and advantages of the present invention will be more clearly understood by reference to the following detailed description and examples.

In accordance with the present invention it has been found that a mixture of granular petroleum asphalts wherein the softening point of the asphalt compounds differ by at least 25 F. as measured by ASTM Method E-28-51-T are excellent materials for the insulation and protection of metallic structures such as pipe linesand the like. Ithas also been found in accordance with the present invention that these mixtures of petroleum asphalts may be further modified to include porous inorganic materials such as expanded volcanic materials of the nature of perlite, volcanic ash, obsidian, tuft and the like and porous inorganic aggregates such as expanded vermiculite, haydite, pumice, scoria, etc.

Asphalts suitable foruse in accordance with the presenf invention include modified and unmodified asphaltic materials derived from petroleum. Various methods for separating asphalts from petroleum containing the same and formodifying such asphalts are well known to those skilled in the art and therefore the detailed description of such methods will not be repeated here since these methods form no part of the present invention. One method of obtaining petroleum asphalts is by extracting crude petroleum containing asphaltic materials with solvents such as propane. In general, these extracted asphalts have softening points in the neighborhood of approximately 170 F. The extracted asphalt may thereafter be treated by conventional oxidizing procedures to vary the softening point of the asphalt or other physical properties may be likewise varied by, known treating procedures. In general, asphalts suitable for use in accordance with the present invention include materials having softening points in the range of about 150 F. to 500 F. V I

In order to prepare petroleum asphalt for use in accordance with the present invention, the asphaltic material is reduced to granular form by grinding, flaking, and other known methods. The granulated asphalt should have a maximum particle size of about one inch in di ameter and preferably should have a bulk a density of about 30 to 70 pounds per cubic foot. It has been found in accordance with the present invention, that by mixing at least two granulated asphalts having softening points which differ by atleast 25 "F., and preferably 25 F. to200 F., substantially improved results are obtained as compared to the results obtained when the same two asphalts are first fused and then granulated.

The mixture of granulated asphalts may be applied to the metallic structure to be insulated and protected by surrounding the structure with the granulated material and thereafter heating the structure to form a fused zone adjacent the outer surface of the structure and a sintered zone surrounding the fused zone and in some cases Where the nature of the service permits a third zone of loose granular materials surrounding the sintered zone. In the case of the protection of a pipe line which is to be buried in the earth, the pipe is placed in a trench larger than the exterior dimensions of the pipe and is supported above the bottom of the trench. The granular petroleum asphalt mixture is then ponred'in the trench to a height sufficient to cover the pipe and earth is then placed over the granulated asphalt to seal the top of the trench. In general, the thickness of the asphalt mixture around the pipe should be at leastfour inches and for pipes larger than into the trench in granular form to a height of approximately six inches above the top surface of the pipe. Steam at a temperature of 350 F. was then passed through the pipe and the temperature at various distances four inches in diameter the thickness should be equal to from the outer surface of the pipe was measured conthe diameter. Thus, a two-inch pipe would need a fourtinuously. When the temperatures being measured in the inch thick layer around it-but a six-inch pipe would trench had reached substantially constant values, the need a six inch layer for effective insulation. If the pipe steam was cut off and the asphalt surrounding the pipe line in question is to supply a heated fluid, such as steam, was inspected. During this inspection the adhesion of completion of the insulating operation is brought about the asphalt to the pipe was observed, the location'and by merely passing steam through the pipe line. In those depth of any voids surrounding the pipe was observed, cases where the pipe line is to be protected against corrothe thickness of the sintered zones surrounding the fused sion and is to be used for carrying unheated fluids or zone was measured and the thickness of the fused zone gases, the structure is heated by extraneous means such adjacent the pipe was also measured. In addition, obas by steam, hot gases, an electric current or the like in servations were made as to whether the fused zone surorder to form the desired protective zones in the granurounding the pipe was uniform on all sides of the pipe. lated asphaltic mixture surrounding the pipe and thereafter In runs 1 and 2 of Table 1, 100% of an oxidized asphalt heating is discontinued. Regardless of whether the pipe having a softening point of 335 F. and 365 F., respecline or structure is to be employed for hot or cold service tively, were employed alone in granular form. In run 3 systems, the temperature employed to produce the desired a mixture of two asphalts which had first been fused to protective zones in the asphaltic material surrounding the obtain a material having a softening point of 335 F. structure is preferably between the softening points of and then granulated, was employed. Runs 5 through 9, the petroleum asphalts employed, and in those cases inclusive, in Table 1 include the preferred asphalt mixwhere a granular expanded aggregate is present the temtures which form the basis of the present invention and perature is preferably sufiiciently high to melt a portion which were first granulated and then mixed.

Table 1 Temperature at Specified Thickness of Specified Zones Vol. Percent Distance From Pipe, F. Run at and Softening Location and Adhesion Point of Depth of Voids to Pipe Asphalt 0in. 1in. 2m. 3m. 4m. Fused Sinizgred,

1 10075-335 F 350 250 204 160 120 Average 5in.(non-uniiorm). 1% Algiige pipe- Good. 2 100% 365" F 350 248 195 152 122 -..-do 2% Belogipiph Poor. 3 100%-335 F 350 244 192 165 103 Average2in. (non-uniform).-- 1 Algcgdpipe- Good. 4 100%365 F 350 238 182 148 109 Average%ln.(non-uniiorm) 1% B3123 pipe- Poor. 5 {gggjggtl 350 242 193 145 no 1% in. (uniform) 1% None Good. 6 {28 213223 e 242 113 -146 11:; 2 5111. (uniform) 1 (in Do. 7 gggg:ggg: 350 250 195 152 10s 2111. (uniform) 1 do Do. 8 {gggijgggg 350 255 190 141 104 do 1 do Do. 9 e50 256 200 164 119 1% in. (uniform) 1 ----do D0.

of the asphalt having the higher softening point. Of It is to be observed from the data reported in Table 1 course in the case of a structure which is to contain or 50 that in those cases in which a single granulated asphalt or transmit hot fluids, the temperature of heating of the a prefused mixture of asphalts was employed extremely structure is preferably the same as the temperature of the poor results were obtained. In some caess the fused zone fluids contained or transmitted by the structure. As has was either too thin or too thick and in some cases the adbeen pointed out heretofore, it has been found that a hesion to the pipe was poor. In addition, in allcases mixture of granulated petroleum asphalts having softening where a single asphalt or a prefused mixture of asphalts points which differ by at least 25 F. are substantially was employed, the fused zone surrounding the pipe was superior to either component of the mixture or to a mixnon-uniform, in some cases being thinner at the top than ture of the asphalts which has first been fused and then at the bottom while in some cases the top portion was granulated. As will be seen from the following examples thicker than the bottom, and in addition t e fused zone the ratio of the differing softening point asphalts may contained large void spaces adjacent the pipe either at vary over an extremely wide range. However, where no the top or at the bottom. 0n the other hand, where the expanded aggregate is present a volume ratio of 1:1 is composition of the present invention was applied, adhepreferred and where an expanded aggregate is present the sion to the pipe was good, the thickness of both the fused ratio of total asphalt to expanded aggregate is preferably zone and the sintered zone were adequate, no voids were i thi same general range, Example 1 below clearly present in the fused zone and the fused zone was substanshows the substantially improved results obtained by following the principles of the instant invention.

EXAMPLE I tially uniform on all sides of the pipe.

It has also been discovered in accordance with. the present invention that the asphalt mixtures of the instant invention may be further modified by the incorporation therein of porous aggregate materials such as expanded perlite, expanded vermiculite and the like. -The use of such porous materials in a composition of the present invention serves to further reduce the cost of the insulating and protective materials without reducing the effectiveness of the insulation or protection. In addition, these materials add structural strength to the composition and in some cases additional insulating properties of their own. Where the porous aggregate material is hydrophilic in nature, it is preferable to precoat the aggregate with one 6 v in accordance with the present invention should have a particle size equivalent to the particle size of the asphalt with which it is mixed and should preferably be in the range of about 5 to inch in diameter. t

of the asphalts to be employed, or similar asphalt or 5 Known agents for bonding asphalt porous aggregates asphaltic resin. This coating of the porous material serves may also be employed in the practice of the present invento water-proof the material and also raise the density of tion without departing from the spirit thereof. In addithe porous material thus preventing stratification when tion, the expanded inorganic material may be coated by the mixture is poured into a trench or other container. contact with cut back asphalt, with asphalt emulsions, or Various methods of coating coarse aggregate materials are 10 in any other manner known to the art. .known in the art and form no part of the instant invention. We claim: Suitable methods include adding melted or powdered as- 1. A composition for the insulation and protection of phalt to the hot porous material, tumbling the porous ma'-, metallic structures comprising a first granular petroleum terial in a melted asphalt or other known means of coatasphalt and a granular expanded perlite coated with a ing. In some instances where the porous material con- 5 second petroleum asphalt, the volume ratio of total astains interconnected pore spaces, it is often desirable to phalts to perlite being approximately 1:1, said first and mix porous material with water or a volatile solvent prior said second petroleum asphalts being characterized by to coating to prevent the asphalt from entering and filling having ASTM softening points in the range of 150 F. to the pores of the aggregate. As has been indicated above, 500 F. and separated from one another by at least 25 F. the coating material may be either the asphalt having the and the volume ratio of the higher softening point asphalt higher softening point or the asphalt having the lower to the lower softening point asphalt ranging between 10:1 softening point. The coated porous material is 'then and 1:1, said composition being further characterized by mixed with the other asphalt employed in accordance with forming a plastic zone immediately adjacent the outer the present'invention or with an additional amount of the surface of said structures, a sintered zone surrounding said asphalt which has been used in coating, which is in plastic zone andazone of loose granules surrounding said granular form, plus a second asphalt having a softening s n e on when Said composition is heated to a mpoint differing from the coating asphalt by at least 25 F. perature sufficiently high to melt a portion of the asphalt. The use of a mixture of two asphalts having softening 2. A composition for the insulation and protection of points which differ by at least 25 F. in which one asphalt und g nd steam conduits comprising granular particles has been used to coat a porous aggregate material is i1- of a first petroleum asphalt, and a granular expanded lustrated in Example II below. 1 perlite coated with a second petroleum asphalt, the volume ratio of the total asphalts to perlite being approximately EXAMPLE II 1:1, said first and said second petroleum asphalts being The procedure followed in Example I above was recharacterized by having ASTM softening points separated peated in the present example, except that the lower from one another by at least 25 F. and spanning the softening point asphalt was employed to coat an inorganic temperature of said steam conduit, the volume ratio of the granular material. As is obvious from Table 2 below, in higher softening point asphalt to the lower softening point runs 1 and 2 a granular expanded perlite was coated with asphalt ranging between 10:1 and 1:1, 'said composition an asphalt having a softening point of 185 F. and was being further characterized by forming-a plastic zone imthen mixed with a second asphalt having a softening point 40 mediately adjacent the outer surface of said steam conwhich exceeds that of the first by at least 25 F. In run duit, a sintered zone surrounding said plastic zoneand a 3 of Table 2 a 185 F. softening-point asphalt was emzone of loose granules surrounding said sintered zone ployed to coat sand and the coated sand was then mixed when said composition is at the temperature of the steam with an asphalt having a softening point of 325 F. The conduit. 1

Table 2 Vol. Percent Temperature at Specified Thickness of Specified Zones and Softening Vol. Percent of I Distance from Pips, F. Location and Adhesion Run# 1221111211); Aggregate j 7 Depth of Voids To Pipe Comgonents 0 in. 1 in. 2 in. 3 in. 4 in. Fused Sintered 1 g2 Z ,g,, f;;}% 1 a11te-- 350 212 212 135 1%111. (uniform) 1 in".-- 'None Good. 2 ..l 9 i:} do sec 254 202 178 134 -----do 1% in-.-

no. 3 {9 'Z3 }4s%-s nd 350 25s 215 182 125 P3553553? }None-.. g;: Do.

same measurements and observations made in Example I References Cited in the file of this patent were repeated in the instant example. UNITED STATES PATENTS It is to be observed from a study of the results reported in Table 2 that the mixture of precoate'd sand and asphalt 5 "5" 1926 ownard Mar. 13, 1928 was substantially inferior to the mixture of precoated 1736 915 memann Nov 26 1929 perlite and asphalt. In the case of the composition con 1 773 461 Nicholson Oct 14 1930 taining sand, the top surface of the pipe was complet 2:332:219 Harshberger Oct. 19: 1943 exposed, no sintered zone existed and a highly non- 2,445,903 Bright 10 1948 uniform fused zone averaging approximately 3 /2 inche 2,625,512 Powell Jan. 13, 1953 was found- 2,634,208 Miscall Apr. 7, 1953 i The porous inorganic material which may be employed 2,668,125 Baker et a1 Feb. 2, 1954 

1. A COMPOSITION FOR THE INSULATION AND PROTECTION OF METALLIC STRUCTURES COMPRISING A FIRST GRANDULAR PETROELUM ASPHALT AND A GRANULAR EXPANDED PERLITE COATED WITH A SECOND PETROLEUM ASPHALT, THE VOLUME RATIO OF TOTAL ASPHALTS TO PERLITE BEING APPROXIMATELY 1:1, SAID FIRST AND SAID SECOND PETROLEUM ASPHALTS BEING CHARACTERIZED BY HAVING ASTM SOFTENING POINTS IN THE RANGE OF 150*F. TO 500*F. AND SEPARATED FROM ONE ANOTHER BY AT LEAST 25*F. AND THE VOLUME RATIO OF THE HIGHER SOFTENING POINT ASPHALT TO THE LOWER SOFTENING POINT ASPHALT RANGING BETWEEN 10:1 AND 1:1, SAID COMPOSITION BEING FURTHER CHARACHERTIZED BY FORMING A PLASTIC ZONE IMMEDIATELY ADJACENT THE OUTER SURFACE OF SAID STRUCTURES, A SINTERED ZONE SURROUNDING SAID PLASTIC ZONE AND A ZONE OF LOOSE GRANULES SURROUNDING SAID SINTERED ZONE WHEN SAID COMPOSITION IS HEATED TO A TEMPERATURE SUFFICEINTLY HIGH TO MELT A PORTION OF THE ASPHALT. 